To satisfy the growing demands for wireless data traffic since commercialization of a 4th generation (4G) communication system, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. That is why the 5G or pre-5G communication system is called a beyond 4G network communication system or a post long term evolution (post LTE) system.
To achieve high data rates, deployment of the 5G communication system in a millimeter wave (mmWave) band (for example, 60 GHz) is under consideration. In order to mitigate propagation path loss and increase a propagation distance in the mmWave band, beamforming, massive multiple input multiple output (massive MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large-scale antenna technologies have been discussed for the 5G communication system.
Further, to improve a system network, techniques such as evolved small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-point (CoMP), and interference cancelation have been developed for the 5G communication system.
Besides, advanced coding modulation (ACM) techniques such as hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC), and advanced access techniques such as filter bank multi carrier (FBMC) and non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) have been developed for the 5G communication system.
To increase the system capacity of a wireless communication system, techniques for increasing the number of antennas in a base station (BS) have been developed. A multi-antenna system may increase system capacity significantly by facilitating multi-user MIMO (MU MIMO) transmission through an array gain of antennas.
For implementation of a multi-antenna system, a transmitter (for example, a BS) needs channel information about a receiver (for example, a user equipment (UE)) to which the transmitter is to transmit a signal. In a frequency division dulplex (FDD) wireless network, the receiver estimates channel information and then feeds back the estimated channel information to the transmitter in order to provide channel information needed for the transmitter. Specifically, the receiver estimates channel information using a reference signal (RS) received on a downlink, quantizes the estimated channel information, and feeds back the quantized channel information to the transmitter.
In a long term evolution-advanced (LTE-A) system, the receiver uses channel state information RSs (CSI-RSs) for channel estimation. The CSI-RSs are designed to use resources orthogonal between antennas, for accurate channel estimation. Due to the orthogonal feature of the CSI-RSs, more antennas are available in the LTE-A system. However, more resources are also used for CSI-RS transmission in proportion to an increase in the number of antennas.